Question : DNS Forwarders on Domain Controllers

I have two domain controllers one Windows 2003, one windows 2008 running AD integrated DNS.  The windows 2003 DC is configured with my ISP's DNS as DNS forwarders.  My Windows 2008 DC shows my Windows 2003 DC as the forwarder.  My question is what should the forwarders on my other domain controller be?  If I lose my first DC there is no forwarder available for the second DC and consequently I would expect external name resolution to fail.  If I add my ISP's DNS servers into the forwarders tab on my Windows 2008 DC it shows a red x.  What is considered best practice for configuring the forwarders on multiple domain controllers?  Should they all the ISP's DNS servers listed?

Answer : DNS Forwarders on Domain Controllers

Yes, you would alos want your other DNS server to use your ISP DNS servers as its forwarders.  When internal clients request an external website like google.com, they will first query your internal DNS server which will then forward the request to the ISP DNS servers for an answer.  If your second DNS server simply forwards the request to your first DNS server to then go out to the Internet, it's simply a waste of time (not that DNS traffic typically tends to take up much network bandwidth - less than ~1%).

As a best practice, simply ensure that you have multiple DNS servers listed as your forwarders in case one does fail.

Hope this helps...

Mike